The present invention concerns a method for making a cross tie for a vehicle chassis, according to which method the vehicle chassis is made at least partially of composite material.
By composite material is meant here a plastic such as polyester, reinforced with fibres, in particular glass fibres, carbon fibres, aramid fibres and such.
With their far ends, the cross ties are for example glued to longitudinal runners made of composite material or to trestles which are also made of composite material and with which the cross ties are carried by wheels.
A known method whereby cross ties are made of composite material is described in Belgian patent No. 1.010.366.
Cross ties are made consisting of a round, tubular body which is provided with round flanges on both ends. The body is made by means of pull winding or filament winding, whereas the flanges are made by means of what is called hot press moulding and are glued to the body.
Pull winding is a method whereby one or several layers of reinforcement fibres are wound on an arbor which are soaked with plastic, either before and/or after the plastic is applied in its liquid state, after which the whole is pulled through an extrusion nozzle, and the plastic cures.
Filament winding is a method of whereby reinforcement fibres or ribbons soaked with plastic are wound on a rotating arbor or cylinder, after which the plastic cures.
In the case of hot press moulding, plastic and reinforcement fibres, possibly in the shape of a pre-impregnated fibre mat, are put in a heated mould and are pressed in the required shape under a very large pressure, for example of 100 tons/m2, and they are cured.
It was found that, especially when the vehicle contains a superstructure on the chassis, the above-mentioned known cross ties sometimes cannot resist the torques to which they are subjected when said vehicle takes a bend.
The invention aims to provide a method for making a cross tie with which is obtained a cross tie which remedies the above-mentioned disadvantages and which cannot only resist the bending forces well, but which can also resist the torques particularly well.
This aim is reached according to the invention in that the cross tie is made with an almost cylindrical centre part and a part connected to both ends thereof which widens towards the end of the cross tie, whereby the above-mentioned parts are made in one piece by means of filament winding, and the filaments are provided in the central part at an angle which is larger than 45xc2x0 in relation to the longitudinal direction of the cross tie, and whereby they are transformed into an angle which is smaller than 45xc2x0 in the widening parts.
In the centre part, filaments can be provided in two directions which cross one another which are directed clockwise and anticlockwise respectively at an angle which is larger than 45xc2x0 but smaller than 80xc2x0 in relation to the longitudinal direction of the cross tie.
Preferably, at least one hard piece, for example a flange, is provided on the broadest end of the widening parts, worked into the composite material.
In this piece can be provided one or several openings in which a thread is tapped.
In these openings can be screwed bolts with which the cross ties are retained in relation to a part such as a longitudinal runner or a trestle of the vehicle chassis as the glue hardens, with which this end is glued to a longitudinal runner or a trestle.
The invention also concerns a vehicle chassis provided which at least one cross tie made according to any of the preceding embodiments, whereby the widening parts of this cross tie are glued with their ends to parts made of composite material of the chassis, for example directly to two longitudinal runners or to two trestles which are connected to these longitudinal runners.